Systems and Methods for Performing Spine Surgery

ABSTRACT

Systems and methods for a spinal surgical procedure are described. Specifically systems and methods for calculating global spinal alignment are described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and is a continuation of U.S.application Ser. No. 15/440,991, filed on Feb. 23, 2017 (currentlypending), which claims priority to and is a continuation ofInternational Patent. Application. No. PCT/US17/14626, filed on Jan. 23,2017. International Patent. Application. No. PCT/US17/14626 claims thepriority of U.S. Provisional Application Ser. No. 62/286,166, filed onJan. 22, 2016. All of the foregoing related applications areincorporated herein by reference in their entireties.

FIELD

The present application pertains to spinal surgery. More particularly,the present application pertains to systems and methods related to theplanning, performing, and assessing of surgical correction to the spineduring a spinal procedure.

BACKGROUND

The spinal column is a highly complex system of bones and connectivetissues that provide support for the body and protect the delicatespinal cord and nerves. The spinal column includes a series of vertebralbodies stacked atop one another, each vertebral body including an inneror central portion of relatively weak cancellous bone and an outerportion of relatively strong cortical bone. Situated between eachvertebral body is an intervertebral disc that cushions and dampenscompressive forces exerted upon the spinal column. A vertebral canalcontaining the spinal cord is located behind the vertebral bodies. Thespine has a natural curvature (i.e., lordosis in the lumbar and cervicalregions and kyphosis in the thoracic region) such that the endplates ofthe upper and lower vertebrae are inclined towards one another.

There are many types of spinal column disorders including scoliosis(abnormal lateral curvature of the spine), excess kyphosis (abnormalforward curvature of the spine), excess lordosis (abnormal backwardcurvature of the spine), spondylolisthesis (forward displacement of onevertebra over another), and other disorders caused by abnormalities,disease, or trauma (such as ruptured or slipped discs, degenerative discdisease, fractured vertebrae, and the like). Patients that suffer fromsuch conditions often experience extreme and debilitating pain, as wellas diminished nerve function. Posterior fixation for spinal fusions,decompression, deformity, and other reconstructions are performed totreat these patients. The aim of posterior fixation in lumbar, thoracic,and cervical procedures is to stabilize the spinal segments, correctmulti-axis alignment, and aid in optimizing the long-term health of thespinal cord and nerves.

The definition and scope of spinal deformity, as well as treatmentoptions, continue to evolve. Surgical objectives for spinal deformitycorrection include curvature correction, prevention of furtherdeformity, the restoration of sagittal and coronal balance, cosmeticoptimization, and improvement or preservation of neurological function.Sagittal plane alignment and pelvic parameters in cases of adult spinaldeformity (ASD) are becoming increasingly recognized as correlative tohealth related quality of life scores (HRQOL). In the literature thereare significant correlations between HRQOL scores and radiographicparameters such as Sagittal Vertical Axis (SVA), Pelvic Tilt (PT) andmismatch between pelvic incidence (PI) and lumbar lordosis (LL).Specific cervical parameters, including cervical lordosis (CL), cervicalsagittal vertical axis (CSVA), T1 slope (TS), and the chin-brow verticalangle (CBVA), are significant indicators of the body's ability, or lackthereof, to align the head over the pelvis and maintain a horizontalgaze.

The SRS-Schwab classification of ASD was developed to assist surgeonswith a way to categorize ASD, and provide methods of radiographicanalysis. This classification system helps provide a protocol forpre-operative treatment planning and post-op assessment. The currentenvironment to utilize this classification system requires surgeons toexamine pre-operative patient films and measure pelvic incidence, lumbarlordosis, pelvic tilt, and sagittal vertical axis either manually orthrough the use of pre-operative software. After the procedure, thesurgeon examines the post-operative films and measures the sameparameters and how they changed as a result of the surgery. A needexists for systems and methods for assessing these and other spinalparameters intraoperatively and assessing changes to theseintraoperative spinal parameters as a surgical procedure progressestowards a pre-operative plan.

Screws, hooks, and rods are devices used to stabilize the spine during aspinal fixation procedure. Such procedures often require theinstrumentation of many bony elements. The devices, for example rods,can be extremely challenging to design and implant into the patient.Spinal rods are usually formed of stainless steel, titanium, cobaltchrome, or other similarly hard metal, and as such are difficult to bendwithout some sort of leverage-based bender. Moreover, a spinal rod needsto be oriented in six degrees of freedom to compensate for theanatomical structure of a patient's spine as well as the attachmentpoints (screws, hooks) for securing the rod to the vertebrae.Additionally, the physiological problem being treated as well as thephysician's preferences will determine the exact configurationnecessary. Accordingly, the size, length, and particular bends of thespinal rod depends on the size, number, and position of each vertebraeto be constrained, the spatial relationship amongst vertebrae, as wellas the screws and hooks used to hold the rods attached to the vertebrae.

The bending of a spinal rod can be accomplished by a number of methods.The most widely used method is a three-point bender called a FrenchBender. The French bender is a pliers-like device that is manuallyoperated to place one or more bends in a rod. The French bender requiresboth handles to operate and provides leverage based on the length of thehandle. The use of the French bender requires a high degree of physicianskill because the determination of the location, angle, and rotation ofbends is often subjective and can be difficult to correlate to apatient's anatomy. Other methods of bending a rod to fit a screw and/orhook construct include the use of an in-situ rod bender and a keyholebender. However, all of these methods can be subjective, iterative, andare often referred to as an “art.” As such, rod bending and reductionactivities can be a time consuming and potentially frustrating step inthe finalization of a complex and/or long spinal construct. Increasedtime in the operating room to achieve optimum bending can be costly tothe patient and increase the chance of the morbidity. When rod bendingis performed poorly, the rod can preload the construct and increase thechance of failure of the fixation system. The bending and re-bendinginvolved can also promote metal fatigue and the creation of stressrisers in the rod.

Efforts directed to computer-aided design or shaping of spinal rods havebeen largely unsuccessful due to the lack of bending devices as well aslack of understanding of all of the issues involved in bending surgicaldevices. Recently, in U.S. Pat. No. 7,957,831, issued Jun. 7, 2011 toIsaacs, there is described a rod bending system which includes a spatialmeasurement sub-system with a digitizer to obtain the three dimensionallocation of surgical implants (screws, hooks), software to convert theimplant locations to a series of bend instructions, and a mechanical rodbender used to execute the bend instructions such that the rod will bebent precisely to custom fit within each of the screws. This isadvantageous because it provides quantifiable rod bending steps that arecustomized to each patient's anatomy enabling surgeons to createcustom-fit rods on the first pass, thereby increasing the speed andefficiency of rod bending, particularly in complex cases. This, in turn,reduces the morbidity and cost associated with such procedures. However,a need still exists for improved rod bending systems that allow forcurvature and deformity correction in fixation procedures, provide theUser with more rod bending options, and accommodate more of the User'sclinical preferences. Furthermore, a need exists for improved rodbending systems that ensure proper sagittal and coronal alignment of thespine so that patients' HRQOL can be enhanced over standard methods.

SUMMARY

The needs above, as well as others, are addressed by embodiments of asystem and method for displaying near-real time intraoperative images ofsurgical tools in a surgical field described in this disclosure.

A system is disclosed for global alignment of a spine during spinesurgery, where the system includes an imaging device, a spatial trackingsystem, a control unit, and a bending device.

A system is disclosed for global alignment of a spine during spinesurgery, where the system includes an imaging device, a rod bendingdevice, and a control unit with software to enable entry of spinalparameter measurements from preoperative images, surgical planning, andintraoperative images, and generating instructions for bending a rod.The anatomical parameter may be chin brow vertical angle. The parametermay be related to the patient's gaze. The parameter may be related tothe patient's quality of life score. The system may further providevisual indicators regarding the measured parameters.

A method is disclosed for global alignment of a spine during spinesurgery, wherein the method includes inputting surgical plan parametersinto a control unit, taking intraoperative measurements of theparameters, comparing the intraoperative measurements to the surgicalplan, measuring the location of the bone screws, calculating rod bendinginstructions, and bending the rod according to the instructions. Theparameter may be chin brow vertical angle. The parameter may be relatedto the patient's gaze. The parameter may be related to the patient'squality of life score.

BRIEF DESCRIPTION OF THE DRAWINGS

Many advantages of the present invention will be apparent to thoseskilled in the art with a reading of this specification in conjunctionwith the attached drawings, wherein like reference numerals are appliedto like elements and wherein:

FIG. 1 is a diagram of a system for measuring spinal parametersaccording to one embodiment;

FIG. 2 is a screen shot illustrating an example of a mobile device withapplication software for preoperative measurements according to oneembodiment;

FIG. 3 is a screen shot illustrating an example of the a setup screenaccording to the embodiment of FIG. 2 to allow the user to capture a newimage or open a saved image;

FIG. 4 is a screen shot illustrating an example of the a setup screenaccording to the embodiment of FIG. 2 to allow the user to specify theimage type;

FIG. 5 is a screen shot illustrating an example of the a setup screenaccording to the embodiment of FIG. 2 to allow the user to identify theorientation of the image;

FIG. 6 is a screen shot illustrating an example of the a setup screenaccording to the embodiment of FIG. 2 to allow the user to enter thescale size;

FIG. 7 is a screen shot illustrating an example of the a setup screenaccording to the embodiment of FIG. 2 to allow the user to set the scaleto the image;

FIG. 8 is a screen shot illustrating an example of the a setup screenaccording to the embodiment of FIG. 2 to allow the user to set the scaleto the image;

FIG. 9 is a screen shot illustrating an example of a measurement screenaccording to the embodiment of FIG. 2 to allow the user to identify theC2 endplate;

FIG. 10 is a screen shot illustrating an example of a measurement screenaccording to the embodiment of FIG. 2 to allow the user to identify themidbody of C2;

FIG. 11 is a screen shot illustrating an example of a measurement screenaccording to the embodiment of FIG. 2 to allow the user to identify theT1 endplate;

FIG. 12 is a screen shot illustrating an example of a measurement screenaccording to the embodiment of FIG. 2 to allow the user to identify theposterior point of C7;

FIG. 13 is a screen shot illustrating an example of a measurement screenaccording to the embodiment of FIG. 2 displaying the calculatedparameters;

FIG. 14 is a flowchart of an integrated alignment according to oneembodiment;

FIG. 15 is a screen shot illustrating an example of a setup screenaccording to one embodiment;

FIG. 16 is a screen shot illustrating an example of system parametersettings according to the embodiment of FIG. 15.

FIG. 17 is a screen shot illustrating an example of a measurement inputsetup screen according to the embodiment of FIG. 15.

FIG. 18 is a screen shot illustrating an example of an image capturescreen according to the embodiment of FIG. 15.

FIG. 19 is a screen shot illustrating an example of an image importedinto the system according to the embodiment of FIG. 15.

FIGS. 20-21 are screen shots illustrating an example of orientation ofthe figure according to the embodiment of FIG. 15.

FIG. 22 is a screen shot illustrating an example of the oriented imageaccording to the embodiment of FIG. 15.

FIG. 23 is a screen shot illustrating an example of importing of asecond image according to the embodiment of FIG. 15.

FIGS. 24-26 are screen shots illustrating an example measurement ofcervical lordosis according to the embodiment of FIG. 15.

FIGS. 27-29 are screen shots illustrating an example measurement of T1slope according to the embodiment of FIG. 15.

FIGS. 30-34 are screen shots illustrating an example measurement ofcervical sagittal vertical axis according to the embodiment of FIG. 15.

FIGS. 35-39 are screen shots illustrating an example measurement of chinbrow vertical angle according to the embodiment of FIG. 15.

FIG. 40 is a screen shot illustrating an example a definitions screenaccording to the embodiment of FIG. 15.

FIG. 41 is a perspective view of one embodiment of a digitizer array inthe closed position comprising part of the system of FIG. 1;

FIG. 42 is an exploded perspective view of the digitizer array of FIG.41;

FIG. 43 is a perspective view of the digitizer array of FIG. 2 in theopen position;

FIG. 44 is a front view of one embodiment of a digitizer pointerassembly comprising part of the system of FIG. 1;

FIG. 45-48 are perspective views of various surgical pointers compatiblewith the digitizer array of FIG. 41;

FIG. 49 is a flow chart depicting the rod bending workflow according toone embodiment;

FIG. 50 is a screen shot illustrating an example setup screen accordingto one embodiment;

FIG. 51-52 are screen shots illustrating an example of the screwacquisition screen according to one embodiment;

FIG. 53 is a screen shot illustrating an example of the rod previewscreen according to one embodiment;

FIG. 54 is a screen shot illustrating an example rod bending instructionscreen according to one embodiment;

FIG. 55 a flow chart depicting the rod bending workflow according toanother embodiment;

FIG. 56 is a screen shot illustrating an example of the Pointsadjustment menu screen according to one embodiment;

FIG. 57 is a screen shot illustrating an Points Adjustment screenaccording to one embodiment;

FIGS. 58-59 are screen shots illustrating an example rod lordosiscorrection screen according to one embodiment;

FIG. 60 is a screen shot illustrating an example of the rod previewscreen with lordosis correction according to one embodiment;

FIGS. 61-62 are screen shots illustrating an example CoronalStraightening screen according to one embodiment;

FIGS. 63-64 are screen shots illustrating an example Transition Rodscreen according to one embodiment;

FIG. 65 is a screen shot illustrating an example of the rod previewscreen for a transition rod according to one embodiment;

FIG. 66 is a screen shot illustrating an example rod bending instructionscreen for a transition rod according to one embodiment;

FIGS. 67-68 are screen shots illustrating an example Offset Connectorscreen according to one embodiment;

FIG. 69 is a screen shot illustrating an example of the rod previewscreen for an offset connector according to one embodiment;

FIG. 70 is a perspective view of a mechanical rod bender according toone embodiment;

FIG. 71 is a flow chart for a method of global spinal alignment,

DETAILED DESCRIPTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin development of any such actual embodiment, numerousimplantation-specific decisions must be made to achieve the developers'specific goals such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure. The systems and methods disclosed herein boast avariety of inventive features and components that warrant patentprotection, both individually and in combination.

Implants placed at one level of the spine to correct a spinal deformitymay affect clinical parameters not only at that site, but also othersites throughout the spinal column. For example, correction of lumbarlordosis may result in a change in cervical lordosis. In some spinalprocedures (e.g., anterior column deformity correction procedures),restoring a patient's spine to a balanced position may be a desiredsurgical outcome. According to a broad aspect of the invention, as shownin FIG. 1 by way of example, one embodiment of a surgical planning,assessment, and correction system 10 may include a spatial trackingsystem 12 to obtain the location of one or more surgical implants 14, acontrol unit 16 containing software convert spinal parameters andimplant locations to a series of bend instructions, a bending device 18to execute the bend instructions, a c-arm fluoroscope for imaging, 20.In some embodiments, the system may also comprise a hand-held mobilecommunication device 15 with application software for makingpreoperative measurements.

The system 10 may include a Global Spinal Balance feature in which thecontrol unit 16 is configured to receive and assess 1) preoperativespinal parameter measurements; 2) target spinal parameter inputs; 3)intraoperative spinal parameter inputs; and 4) postoperative spinalparameter inputs. One or more of these inputs may be tracked and/orcompared against other inputs to assess how the surgical correction isprogressing toward a surgical plan, assess how close the patient's spineis to achieving global spinal balance, and utilized to develop/refine anoperative plan to achieve the desired surgical correction.

The target spinal parameter measurements may be a clinical guideline (byway of example only, the SRS-Schwab classification, or apatient-specific goal based on that patient's anatomy). Depending onUser preference, these spinal parameters may comprise Pelvic Incidence(PI), Pelvic Tilt (PT), Sacral Slope (SS), Lumbar Lordosis (LL),Superior Lumbar Lordosis (↑ LL), Inferior Lumbar Lordosis (↓LL), C7Plumb Line offset (C7PL), and Thoracic Kyphosis (TK), T1 slope (TS),Sagittal Vertical Axis (SVA), cervical lordosis (CL), cervical sagittalvertical axis (CSVA), and chin-brow vertical angle (CBVA) measurements.

Preoperative Measurement

According to the exemplary embodiment shown in FIGS. 2-13, preoperativemeasurement of spinal parameters may be made using a hand held mobiledevice with a camera and a touch screen such as, for example, a mobilephone or a tablet with a software application that includes themeasurement features described below. One such appropriate applicationis Nuvaline®. However any application capable of performing the imagemanipulation and measurements described herein may be used.

As shown in FIG. 2, in one embodiment, the User initiates theapplication by selecting the application icon 102 from the touchscreenof the mobile device. From the list screen, as shown for example in FIG.3, the User may choose to capture a new image by selecting the Newbutton 104, or may view previously captured images and measurements byselecting a previously saved file 106. If the User selects the Newbutton 104, a new image may be captured from a display using the camerafeature of the mobile device 15. As shown in FIGS. 4-8, beforemeasurements can be taken, the User must identify the type andorientation of the image, and provide scale information. The User mayclassify the type of image by selecting the appropriate settings asshown in FIG. 4. If performing preoperative measurements of a cervicalimage, the User may select the Pre Op 108 and Cervical 118 options fromthe setup screen. The User then identifies the orientation of the imageby selecting the correct orientation button 122, 124 as shown in FIG. 5.The length of the measurement calibration scale is entered into thescale field 126 using the keypad 128 as shown in FIG. 6. In thisexample, the scale is set to 5 cm. The User may then correlate the scaleto the imported image by selecting the correct measurement interval onthe screen. As shown in FIGS. 7-8, to mark the Start of Scale 136 acrosshair indicator 146 is placed over the scale 140 located at thebottom of the image, the crosshair indicator 146 may be dragged to thecorrect position by the User's finger. The User then marks the End ofScale 138 by dragging a second crosshair indicator 146 to theappropriate endpoint of the scale on the image 140. In the example shownin FIG. 8, the 5 cm scale has been correlated to the image by choosingpoints 5 cm apart on the image scale 140. When the User selects the Nextbutton 142, the measurement application begins a workflow of measurementinstructions.

As shown in FIG. 9, the User may first mark the location of the C2endplate. Using the bubble with the zoom perspective 134, the User maydrag the crosshairs 146 to a position at the top center of the superiorendplate of C2. Using two fingers, the User may adjust the orientationof the line 148 until it is superimposed over the slope of the C2endplate. The User may press the Next button 142 to advance to the nextmeasurement screen.

As shown in FIG. 10, the User may next mark the location of the C2mid-body. Using the bubble with the zoom perspective 134, the User maydrag the crosshairs 146 to a position on the center of the mid-body ofthe C2 vertebral body. The User may press the Next button 142 to advanceto the next measurement screen.

The User may then mark the T1 endplate as shown in FIG. 11. Using thebubble with the zoom perspective 134, the User may drag the crosshairs146 to a position at the center of the superior endplate of T1. Usingtwo fingers on the touchscreen of the handheld device, the User mayrotate the line 148 until it is superimposed over the slope of the T1endplate. The User may press the Next button 142 to advance to the nextmeasurement screen.

As shown in FIG. 12, the User may mark the posterior of the C7 vertebrain the same manner as the other points. Using the bubble with the zoomperspective 134, the User may drag the crosshairs 146 to a position onthe posterior corner of the C7 endplate. The User may press the Nextbutton 142 to advance to the next measurement screen.

When the spinal markers have been identified, the cervical parametersmay be calculated based upon the locations. The cervical parameterscalculated from the measurements described above may include TS, CL,TS-CL, and CSVA. In some embodiments, the image may be superimposed withlines and angles to provide a graphic rendering of the spinalparameters. For example, in the image shown in FIG. 13, a wedge shapeindicating TS 150 and a wedge shape indicating CL 152 graphicallyrepresent those measurements on the image. The numeric values of themeasurements may be shown in a display area 154 below the image.

In some embodiments, the numeric data may be color-coded to provide anindication of the degree of pathology. The value of TS-CL may bedisplayed, for example, in a Green color when the value isnon-pathologic (TS-CL<+/−15 degrees), in a Yellow color when the valueindicates there is a potential moderate deformity (+/−15≤TS≤+/−20degrees), and in a Red color when the value indicates there is apotential for a marked deformity (TS-CL≥+/−20 degrees). Similarly, thevalue of CSVA may be displayed, for example, in a Green color when thevalue is non-pathologic (CSVA<+/−4 cm), in a Yellow color when the valueindicates there is a potential moderate deformity (+/−4 cm≤CSVA≤+/−8cm), and in a Red color when the value indicates there is a potentialfor a marked deformity (CSVA≥+/−8 cm).

When all measurements have been completed, the User may close the imageby selecting the Check button 156.

It will be appreciated that the embodiment shown in FIGS. 2-13 is merelyexemplary and the methods may be equally applied to other measurements.It will be appreciated that measurements of chin and brow forcalculation of CBVA may be taken using methods similar to thosedisclosed. It will be appreciated that measurements and calculationsrelated to thoracolumbar spinal parameters may be made using methodssimilar to those disclosed. It will be appreciated that the workflow ofmeasurements described in this exemplary embodiment may be performed ina different order. Such modifications may be made without departing fromthe scope of the invention and are within the knowledge of a person ofordinary skill in the art.

Intraoperative Measurement and Global Alignment

In various embodiments, the systems and methods herein measure cervicalparameters and assess both sagittal and coronal balanceintraoperatively, thereby enabling the conversion and transformation ofthe assessment into User actions on the patient. In some embodiments,the systems and methods herein assess the sagittal alignmentintraoperatively. One example embodiment is described below.

In one exemplary embodiment, intraoperative measurement of cervicalspinal parameters may comprise the following steps, each of which usdescribed more fully below: CL may be calculated by acquiring images atC2 and C7, scaling and orienting the images, and identifying the endplates of the C2 and C7 vertebra. TS may be calculated by identifying ahorizontal line along a reticle, and identifying the endplate of T1. TheTS-CL value may be calculated from CL and TS by arithmetic function.CSVA may be calculated by identifying a horizontal line along a reticle,locating the posterior corner of C7, and locating the mid-body positionof C2. Finally, CBVA may be calculated by identifying a vertical line,and locating a point along the brow and chin.

FIG. 14 depicts a flowchart indicating the steps of the Global SpinalBalance feature according to one embodiment. At step 1300 the system 10inputs a patient's preoperative spinal parameter measurements. Then, thesystem 10 generates theoretical target spinal parameter measurements(step 1302). One or more target spinal parameter measurements may beoptionally adjusted the User in accordance with a surgical plan a step1304. At step 1306, a target spinal rod may be scaled to match thepatient's anatomy using the theoretical or adjusted target spinalparameter measurements from step 1302 or 304. This scaled target rod maythen be displayed 1308 to the User. Optionally, the system 10 maygenerate one or more measurements (step 1310) during the surgicalprocedure. At step 1312, the target spinal parameter data may then beadjusted based on the intraoperative measurements from step 310.Finally, the system 10 may generate bend instructions for balanced spinecorrection step 1314.

According to the exemplary embodiment shown in FIG. 15, to begin theintraoperative analysis, the User may initiate the system 10, andidentify a video signal source 404, 406 and video signal type 408, 410.An image may be imported by selecting the import button 418. The image575 displayed in window 420 may be repositioned using the radiuscontrols 414 to enlarge or shrink the image to fit the window 420. Theposition of the image 575 may be changed by use of a directional arrowkeypad 416. The manipulated image may be reset to its original settingby selecting the Reset Image button 412. The user may access a tool menuby selecting the tool button 422, or may select the “?” button 426 toaccess a help menu. As shown in FIG. 16, system settings may be reviewedby selecting the system information screen 400. From this screen a usermay enable the optional CSVA and CBVA measurements by selecting theEnable button 428. The user selects the Return button 424 to return tothe setup menu.

The User may input a patient's preoperative measurements into the system10 as depicted, by way of example in FIG. 17. The User may select theSetup button 432 to access the available parameters. As shown, the Usermay be directed through the process of entering the preoperative data bya setup tool 458. Selecting the Thoracolumbar button 448 may allow theUser to input measurements relevant to thoracolumbar parameters for PI,LL, PI-LL, Seg 1, Seg 2, and TK in fields 550, 552, 554, 556, 558, and560, respectively. Selecting the Cervical button 450 may allow the Userto input measurements relevant to cervical parameters into CL, ΔCL, TS,CSVA, and CBVA input fields (not shown). Preoperative measurements savedto a USB drive may be uploaded to populate the preoperative parametersby selecting the Import USB button 464. The pre-operative measurementsmay be obtained from use of the preoperative measurement softwaredescribed above, or may be calculated within the intraoperative globalalignment software as described below. The pre-operative anatomicalmeasurements may be used to understand the imbalance in the patient'sdeformed spine as well as help determine an operative plan to implantdevices that would adjust or form the spine to a more natural balance(e.g., rods, screws, a hyperlordotic intervertebral implant, etc.).Planning software allows the User to establish a surgical plan tocorrect a spinal deformity. The User may enter the target parameterssought to be achieved through the surgical procedure into the softwarein the same manner as entry of the preoperative values.

In accordance with the Global Spinal Balance feature, spinal parameterinputs may be assessed intraoperatively. For example, the User may wishto intraoperatively measure the amount of cervical lordosis that hasbeen achieved (for example, after placement of an intervertebralimplant). The intraoperative parameter measurements may be compared tothe pre-operative values and the plan to determine if the surgery ishaving the effect of restoring global alignment to the patient. Asdescribed below, the system 10 may be configured to obtain or import oneor more lateral images, generate one or more lines between two or morelandmarks on the patient's anatomy, determine a relationship betweenthose landmarks, and adjust one or more spinal parameters to be used ingenerating the rod solution.

FIGS. 17-27, depict the intraoperative measurement of cervicalparameters according to one embodiment. As shown by way of example inFIG. 17, from the Set-Up screen, the User may first select the Cervicalbutton 450. Next, as shown in FIG. 18, a first lateral radiographicimage 575 may be inputted into the system 10 by selecting the ImportFluoro Image button 418. FIG. 19 shows a representative image of thewindow 420 after an image has been inputted. The images 575 in the leftwindow 478 or right window 480 may be expanded by selecting the + button580 to fill the screen with the selected image. The user may switchbetween the left window 478 and the right window 480 by selecting theimage identification button 582, 584 located above each window. Theimage orientation may be identified by selecting the Orient Image button488. The User identifies the posterior of the patient's anatomy byselecting the appropriate Posterior button 490, as shown for example inFIG. 20. The User identifies the location of the head in the image byselecting the appropriate Head button 498, as shown for example in FIG.21. Once the orientation of the image has been established, it is notnecessary to identify the orientation of subsequent C-arm images unlessthe position of the C-arm is moved during the surgery. The first lateralradiographic image may be moved from the left window 478 to the rightwindow 480 by selecting the Move Image button 488. As shown in FIG. 23,the User may select the Inferior 500 or Superior button 502 to identifywhich cervical segment is captured in the first image. A second lateralradiographic image 575 of the opposite segment, Inferior or Superior,may be inputted into the system 10 as shown in FIG. 23. After theorientation is set, the image identification buttons 582, 584 indicatewhich segment is shown in the image beneath, Superior or Inferior.

According to some embodiments, a User may identify landmarks of thespine by moving lines over at least two points of interest (e.g. thesuperior endplate of V1 and the superior endplate of V2) The system 10then measures the angle between the two lines. For example, as shown inFIGS. 24-26, to calculate CL the User may identify the endplate of C2 inthe superior image and the endplate of C7 in the inferior image. First,a C2 endplate line 802 is placed on the image 575 as shown in FIG. 24.The line 802 is then adjusted to align with the endplates by pressingthe Angle buttons 484 to increase or decrease the angle until the line802 overlays the endplate. As shown in FIG. 25, the system 10 measuresthis angle as 10 degrees as indicated in the angle measurement field474.

Optionally, the system 10 may compare the intraoperative measurement tothe preoperative and/or target spinal parameter value and provide anindication to the User of how much correction has been achieved relativeto the pre-operative and theoretical spinal parameters. As shown in FIG.25, The values in the CL value display window 472 indicate thepreoperative CL was measured at +20 degrees, the planned CL was −5degrees, and the intraoperative CL was measured at +10 degrees.Therefore, the system calculates the change in CL (ΔCL) as 10 degrees asindicated in the measurement field 474. As shown in FIG. 26, the leftwindow 478 has been zoomed and the right window 480 minimized. Toenhance visibility and increase accuracy of the line placement, theimage may be manipulated to increase or decrease the brightness 504 orcontrast 506 by using the + and − buttons. Using the angle measurementbuttons 484, the User may increase the desired angle of correction ofthe spine in the sagittal plane (i.e., add or subtract lordosis orkyphosis). As the angle is adjusted, the amount of adjustment may bedynamically displayed within the angle measurement field 472.

In some embodiments, the User may optionally wish to intraoperativelymeasure a second anatomical or cervical characteristic, such as thepatient's T1 Slope (TS). As shown in FIG. 27, selecting the TSmeasurement button 512 optionally brings up a TS assessment tool. Afluoroscopic image 575 of the patient's cervical spine is inputted intothe system 10. If necessary, the image may be oriented as previouslydescribed. The method of calculating TS is illustrated in FIGS. 28-29.First, as shown in FIG. 28, a horizontal line can 804 be established byuse of a reticle affixed to the c-arm. To establish the line, the Userselects the Reference Point 1 button 514 a in the TS tool 514 and usesthe arrow array 486 to identify a first point 806 on the horizontal line804 of the reticle. Next, the User selects the Reference Point 2 button514 b and uses the arrow array 486 to identify a second point 808 on thehorizontal line 804. Next, as shown in FIG. 29, the User then selectsthe T1 Endplate 1 button 514 c to identify the posterior aspect of theT1 end plate 810. Finally, the User selects the T1 Endplate 2 button 514d and uses the arrow array 486 to identify the anterior aspect of the T1end plate 812. With all TS inputs selected, the control unit 16calculates a line 814 between the posterior 810 and anterior 812 points.The angle between the T1 endplate line 814 and the horizontal line 804can then be measured by the control unit 16, thus resulting in the TSangle. In the example shown in FIG. 29, the system 10 measures thisangle as 45 degrees as indicated in the TS measurement field 470.

From the measured CL and TS, the system 10 may calculate the TS-CLmeasurement and provide color-coded feedback to the User regarding thedegree of deformity. The value of TS-CL may be displayed, for example,in a Green color when the value is non-pathologic (TS-CL<+/−15 degrees),in a Yellow color when the value indicates there is a potential moderatedeformity (+/−15≤TS≤+/−20 degrees), and in a Red color when the valueindicates there is a potential for a marked deformity (TS-CL≥+/−20degrees).

In some embodiments, it may also be desirable to determine theintraoperative cervical sagittal vertical axis (CSVA). This may involvethe use of a reticle and a central radio dense marker 822 placed on thec-arm receiver to allow a true vertical axis to be identified. Selectingthe CSVA button 508 optionally brings up a CSVA tool 516. As shown inFIGS. 30-32, a first fluoroscopic image may be taken of the inferiorcervical region, aligned over C7. The User may first select theReference Point 1 button 516 a and use the arrows to select a firstposition 816 on the line of the reticule. The User then may select theReference Point 2 button 516 b and use the arrows to select a secondposition 818 on the line of the reticule. These reference pointsidentify a vertical line 820. The User then selects the Posterior C7button 516 c, and uses the arrow array 486 to identify the position ofthe posterior corner of the C7 superior end plate 824. The User may thenrelocate the c-arm such that it is aligned over the superior cervicalspine and C2 as shown in FIG. 33. The User aligns the marker 822 andincreases or decreases the diameter of the marker with the markerdiameter buttons 518. After alignment, the User may select the CentroidC2 button 516 f and use the arrow array 486 to identify the midbody ofthe C2 vertebral body 826. The User may move back and forth between theC7 and C2 images by selecting the appropriated button 522, 524. Inalternative embodiments, a single fluoroscopic image may be takenwherein both the C7 and C2 vertebrae are visible in one image. Thevertical line is determined by marking two points on the reticle line.The posterior C7 and centroid C2 are identified as described above. Thesystem 10 may calculate the CSVA measurement and display the values in aCSVA measurement field 520. In some embodiments, the system 10 mayprovide color-coded feedback to the User regarding the degree ofdeformity. The value of CSVA may be displayed, for example, in a Greencolor when the value is non-pathologic (CSVA<+/−4 cm), in a Yellow colorwhen the value indicates there is a potential moderate deformity (+/−4cm≤CSVA≤+/−8 cm), and in a Red color when the value indicates there is apotential for a marked deformity (CSVA≥+/−8 cm). As shown in the CSVAmeasurement field 520 in FIG. 34, the system has calculated CSVA in thepresent example to be +3.5 cm. The system may also display thepre-operative value of CSVA which is shown in this example to be 4 cm.

The chin brow vertical angle (CBVA) may optionally be determined in someembodiments. This can be accomplished by using a guidance reticle, orpositioning two radio dense markers (not shown) at the 12 and 6 o'clockpositions on the c-arm receiver face. Selecting the CBVA button 510optionally brings up a CBVA tool 530. As shown in FIGS. 35-37, afluoroscopic image can be taken of the cranium and oriented as describedabove. The User then establishes a true vertical line as shown in FIG.38. The user may first select the Reference Point 1 button 530 a and usethe arrow array 486 to select a first position 828 on the line of thereticule. The User may then select the Reference Point 2 button 530 band uses the arrow array 486 to select a second position 830 on the lineof the reticule. These reference points identify a true vertical line832. The User then may measure the line between brow and chin as shownin FIG. 39. The User may select the Brow button 530 c, and uses thearrow array to identify a point on the brow 834. The User then selectsthe Chin button 530 d, and uses the arrows to identify a point on thechin 836. The system 10 automatically draws and calculates the anglebetween a line from chin to brow 838 and the vertical axis 832, thusresulting in the CBVA. The value of CBVA may be displayed, for example,in a Green color when the value indicates the patient has an acceptablegaze position relative to the horizon, in a Red color when the valueindicates there is a potential that the patient has an unacceptable gazeposition, too high or too low relative to the horizon, and in a Yellowcolor when the value indicates there is a potential that the patient'sgaze position may be at an intermediate level of acceptability. As shownin the CBVA measurement field in FIG. 39, the system has calculated CBVAin the present example to be −17 degrees. The system may also displaythe pre-operative value of CBVA which is shown in this example to be −15degrees.

FIG. 40 provides an example of a definitions page which may be includedto define the abbreviations for the User.

The User may optionally measure the patient's thoracolumbar parametersto assess global alignment of the spinal column. The method of measuringand calculating thoracolumbar parameters may be any known in the art. Byway of example only, the system and methods for measurement andcalculation of thoracolumbar parameters may be those described in U.S.patent application Ser. No. 15/045, 084 entitled “Systems and Methodsfor Planning, Performing, and Assessing Spinal Correction DuringSurgery” and filed on Feb. 16, 2016, the entire contents of which arehereby incorporated by reference as if set forth fully herein.

Although the methods described above are referred to as intraoperative,it will be appreciated that the same systems and methods are equallyapplicable to pre-operative and post-operative measurements of spinalparameters.

Rod Bending

Referring back to the embodiment of a surgical planning, assessment, andcorrection system 10 as shown in FIG. 1, the system 10 includes aspatial tracking system 12 to obtain the location of one or moresurgical implants 14, a control unit 16 containing software to convertthe implant locations to a series of bend instructions, and a bendingdevice 18 to execute the bend instructions.

Preferably, the spatial tracking system 12 includes an IR positionsensor 20, a digitizer pointer 23, as well as other components includingHost USB converter 21. The spatial tracking system 12 is incommunication with control unit 16. The control unit 16 has spatialrelation software and C-arm video import capabilities and iscommunicatively linked to the display 32 so that information relevant tothe surgical procedure may be conveyed to the User in a meaningfulmanner. By way of example, the relevant information includes, but is notlimited to, spatial positioning data (e.g., translational data in the x,y, and z axes and orientation/rotational data R_(x), R_(y), and R_(z))acquired by the IR position sensor 20 and intraoperative fluoroscopicimages generated by the C-arm fluoroscope.

According to one or more embodiments, the system 10 comprises aneuromonitoring system communicatively linked to the spatial trackingsystem 12 and/or the C-arm via the control unit 16. By way of exampleonly, the neuromonitoring system may be the neuromonitoring system shownand described in U.S. Pat. No. 8,255,045, entitled “NeurophysiologicMonitoring System” and filed on Apr. 3, 2008, the entire contents ofwhich are hereby incorporated by reference as if set forth fully herein.

According to one or more embodiments, the system 10 comprises adigitizer pointer and IR-reflective tracking array component incommunication with the control unit 16. By way of example only, thedigitizer and IR-reflective tracking array system may be the digitizerand IR-reflective tracking array system shown and described in U.S.patent application Ser. No. 13/815,643, entitled “Systems and methodsfor performing spinal surgery” and filed on Mar. 12, 2013, the entirecontents of which are hereby incorporated by reference as if set forthfully herein.

FIGS. 41-48 depict the various components of one or more digitizerpointers 23 for use with the present invention. FIGS. 41-43 detail anexample IR-reflective tracking array 22 component of the digitizerpointer 23. Array 22 includes a housing 34, bilateral shutters 36, and aplurality of IR-reflective spheres 38 arranged in a calculated manner atvarious locations on the array 22 such that their position informationis selectively detectable by the IR position sensor 20. Housing 34comprises a top housing 40, bottom housing 42, and a distal threadedaperture 56 configured to threadably receive the threaded end 78 of astylus (e.g., stylus 24, 26, 28, and/or 30). Top housing portion 40 isfurther comprised of upper portion 44, underside 46, and sides 48. Aplurality of sphere apertures 52 extend between upper portion 44 andunderside 46 and are sized and dimensioned to receive reflective spheres38 within recessed pockets 54. Each side 48 includes cutout 50 sized anddimensioned to receive tongue 70. Bottom housing 42 is comprised of afirst face 58 and a second face 60. The first face 58 includes nestingplatforms 62 and bullet posts 64. Each shutter 36 includes handleportion 66, cover portion 68, tongue 70, interdigitating gear teeth 72,and channel 74 for receiving bullet posts 64. A spring 76 extendsbetween the two shutters 36 and is held in place via spring posts 71.

In an assembled state, each IR-reflective sphere 38 is nested on aplatform 62. Top housing 40 is placed over bottom housing 42 in a snapfit configuration such that each IR-reflective sphere 38 fits within arecessed pocket 54 within its respective sphere aperture 52. Accordingto one implementation, bilateral shutters 36 are positioned over thehousing 34 with tongues 70 sliding into cutouts 50 such that eachshutter cover 68 obscures exactly one half of the IR-reflective sphere38 (for example, the middle IR-reflective sphere 38) as depicted in FIG.43.

As depicted in FIG. 44, the IR-reflective tracking array 22 mates withone or more surgical objects (for example styluses 24, 26, 28, 30). Eachstylus 24, 26, 28, 30 includes a threaded proximal end 78 for matingwith the threaded distal aperture 56 of the IR-reflective tracking array22, elongate shaft 80, and shaped distal tip 82. Shaped distal tip 82may be any shape that is complimentary to, and fits securely within, theshape of a particular screw head. For example, FIGS. 45-48 show styluses24, 26, 28, and 30 each with a different shaped distal tip designed tomate with different open screw systems, minimally-invasive screwsystems, and closed tulip, iliac, and offset connector systems. Thedistal tip 82 is preferably inserted into each screw while orienting thedigitizer pointer coaxial to that screw (or other fixation device).

According to some implementations (for example, the implementationsshown with respect to styluses 24, 26, and 28), the length of theelongate shaft 80 is fixed relative to the array 22 such that alldigitized points are a consistent length from the geometry of theIR-reflective markers 38 and position information may be obtained fromthis relationship. According to other implementations, the length of theelongate shaft 80 is adjustable relative to the array 22 such as thatshown with stylus 30, effectively elongating the distance from thedigitized point and the IR-reflective markers. This longer distancetranslates to digitization of a point above the actual screw head basedon the distance the User adjusted the elongate shaft 80. As will beappreciated in conjunction with the discussion below, the resulting bendinstructions would shape a rod that traverses that point above the screwallowing the User to reduce the screw to the rod.

In accordance with the present invention, there are provided a pluralityof algorithms for achieving rod bends. The surgical bending algorithmsmay be divided into two smaller sub-systems: (1) the spatial locationalgorithms that acquire, collect, and digitize points in space and (2)the bending algorithms that analyze the points and calculate the bendinstructions and rod length needed to bend a rod with the mechanicalbending device 18. U.S. patent application Ser. No. 13/815,643, entitled“Systems and methods for performing spinal surgery” and filed on Mar.12, 2013, the entire contents of which are hereby incorporated byreference as if set forth fully herein, describes such bendingalgorithms in details.

Details of the system 10 are now discussed in conjunction with a firstembodiment of a method for obtaining a custom-fit rod. The system 10 istypically utilized at the end of a posterior or lateral fixationsurgical procedure after screws, hooks or other instrumentation havebeen placed, but prior to rod insertion. As shown in the flowchart ofFIG. 49, the system 10 obtains position information of the implantedscrew positions and outputs bend instructions for a rod shaped tocustom-fit within those implanted screws. At step 1190, pertinentinformation is inputted into the system via a setup screen. At step1192, the User designates the side for which a rod will be created(patient's left or right side). At step 1194, the system 10 digitizesthe screw locations. At step 1196, the system 10 outputs bendinstructions. At step 1198, the User bends the rod according to the bendinstructions. Steps 1190-1198 may then be repeated for a rod on thecontralateral side of the patient if desired.

FIG. 50 illustrates, by way of example only, one embodiment of a screendisplay 200 of the control unit 16 capable of receiving input from aUser in addition to communicating feedback information to the User. Inthis example (though it is not a necessity), a graphical User interface(GUI) is utilized to enter data directly from the screen display 200. Asdepicted in FIG. 50, the screen display 200 may contain a header bar202, a navigation column 204, device column 206, and a message bar 208.

Header bar 202 may allow the User to view the date and time, altersettings, adjust the system volume, and obtain help information via dateand time display 210, settings menu 212, volume menu 214, and help menu216 respectively. Selecting the settings drop-down menu 212 allows theUser to navigate to system, history, and shutdown buttons (not shown).For example, choosing the system button displays the rod bendingsoftware version and rod bender configuration file; choosing theshutdown option shuts down the rod bending software application as wellas any other software application residing on the control unit 16 (e.g.a neuromonitoring software application); and choosing the history optionallows the User to navigate to historical bend points/instruction datain previous system sessions as will be described in greater detailbelow. Selecting the help menu 216 navigates the User to the system Usermanual. As will be described in greater detail below, navigation column204 contains various buttons (e.g., buttons 218, 220, 222, 224, 226) fornavigation through various steps in the rod bending process. Pressingbutton 204 expands/minimizes the details of the navigation column.Devices column 206 contains various buttons indicating the status of oneor more devices associated with the system 10. By way of example,devices column 206 may include button 228 for the digitizer 23 componentof the system 10, respectively. Pressing button 206 expands/minimizesthe details of the devices column. Furthermore, pop-up message bar 208communicates instructions, alerts, and system errors to the User.

Upon selecting setup button 218 on the display screen 200, the system 10automatically initiates the setup procedure. The system 10 is configuredto detect the connection status of each of its required components. Byway of example only, icon 228 indicates the connectivity and activitystatus of the digitizer 23. If one or more required components are notconnected or are connected improperly, the display 200 may alert theUser to address the issue before proceeding via textual, audio, and/orvisual means (e.g., textual messages, audible tones, colored icons orscreens, blinking icons or screens, etc.). According to one embodiment,the digitizer icon 228 is a status indicator for the active acquisitionand/or recognition of the digitizer and the presence and backgroundcolor of the icon 228 may change to indicate the digitizer trackingstatus. By way of example, the icon 228 may be absent when the system 10is not acquiring screws and does not recognize the digitizer, gray whenthe system 10 is not acquiring screws and recognizes the digitizer,green when the system 10 is in screw acquisition mode and recognizes thedigitizer, and red when the system 10 is in screw acquisition mode anddoes not recognize the digitizer. Pressing button 206 expands/minimizesthe details of the device column 206. Depending on the type of surgery,type of patient deformity, etc., it may be advantageous for the User tochoose a digitizer from a selection of different digitizers. Accordingto one embodiment, pressing the stylus icon (not shown) expands apull-out window for the different stylus options available with thesystem 10 (e.g., styluses 22, 24, 26, 30 as described above).

With all of the required components properly connected to the system 10,the User may then input one or more pieces of case-specific informationfrom one or more drop-down menus. By way of example, drop-down menus forrod system 234, rod material/diameter 236, rod overhang 238, proceduretype (not shown), and anatomical spinal levels of the surgicalprocedure) may be accessed from the setup selection panel 232 of thescreen display 200. The rod system drop-down menu 234 allows the User tochoose the rod system he/she plans to use. This selection drives choicesfor the rod material/diameter 236 drop-down menus. By way of example,under the rod system drop-down menu 234, the system 10 may be programmedwith numerous fixation options from one or more manufacturers.Alternatively, it may be programmed with the fixation system selectionsfor one manufacturer only (e.g. NuVasive® Reline™, Precept®, Armada®,and SpherX® EXT). The User may also choose the combination of rodmaterial (e.g. titanium, cobalt chrome, etc.) and rod diameter (e.g. 6.5mm diameter, 5.5 mm diameter, 3.5 mm diameter). The drop-down menu 238for material and diameter options may preferably be dependent upon thechoice of rod system. Because the geometry and sizes can vary betweenmanufacturers and/or rod systems, programming the system 10 with thesespecific inputs can aid in outputting even more accurate bendinstructions. The User may also choose the amount of overhang from therod overhang pull-down menu 238. By way of example, the amount ofoverhang may be selectable in 0 mm, 2.5 mm, 5 mm, 7.5 mm, and 10 mmlengths. According to one embodiment, this function prescribes asymmetric overhang on both the superior and inferior ends of the rod.According to another embodiment, this function also prescribes differentoverhang lengths on either end of the rod based on User preference andpatient anatomical considerations. The system 10 also containsfunctionality for accommodating multiple rod diameters, 5.5 mm to 3.5 mmtransitional rods, and hinged rods as used, for example inOccipital-Cervical-Thoracic (OCT) fusion procedures.

After the setup inputs have been inputted into the setup selection panel232, the system 10 aids the User in setting up the IR sensor 20 in anoptimal position for positional data acquisition. It is to beappreciated that any visual (textual, graphic) indicator may be used toindicate the IR sensor placement instructions. According to someimplementations, an active graphic directs the User to position the IRsensor 20 relative to the digitizer array 22 held static within thepatient's body. As shown in FIG. 50, the User first selects the side ofthe patient the IR sensor 20 is located on by selecting the left sidesensor position button 242 or right side sensor position button 244 inthe IR sensor setup panel 240. Choosing the left or right side sensorposition button 242, 244 activates a the IR sensor positioning panel 246such that sensor graphic 248 and a tracking volume box graphic 250appear on the display screen 200. Tracking volume box 252 that moveswith the sensor graphic 248 as the IR sensor 20 is moved. Next, the Userpositions the digitizer array 22 into the body of the patient. Oncerecognized by the system 10, a target volume box 252 (which may bedisplayed as white in color) is positioned over the patient graphic 254.Next, the User moves the IR sensor 20 relative to the digitizer array 22until the tracking volume box 250 matches up to the position of thetarget volume box 252. According to some implementations, the sensorgraphic 248 increases in size if it is moved superior to the targettracking volume and decreases in size if it is moved inferior to thetarget volume. According to some other implementations, the trackingvolume box 250 may be color-coded to depict the relative distance to thetarget volume. By way of example, the tracking volume box 250 may bedepicted in red if the distance to the target volume is outside of acertain distance in one or more axes (e.g., outside ±8 cm in all 3axes.) and green if within or equal to ±8 cm in all 3 axes. Once theoptimal position of the IR sensor 20 has been ascertained, the setupprocess is complete.

Once the User has completed all of the required steps in the setupscreen, a graphic (e.g., a check) may appear on setup button 218 toindicate such a completion and the system 10 proceeds to step 1192 inthe flowchart of FIG. 49. Using the GUI, the User designates which sideof the patient's spine to acquire digitized positional information fromby selecting either the Left “L” toggle/status button 220 or Right “R”toggle/status button 222. The User then selects the Acquire Screwsbutton 224 which navigates the display screen 200 to an Acquire Screws(left or right) screen shown by way of example in FIGS. 51-52. InAcquire Screws mode, the display screen 200 includes a sagittal viewpanel 256 and a coronal view panel 258 with spine graphics 260, 262 ineach of the sagittal and coronal views, respectively. Spine graphic 260may flip orientation depending on which side of the spine the User isdigitizing (left or right). Additionally, spine graphic 262 mayhighlight the side of the patient the User is digitizing (left orright). The User may digitize the location of each implanted screwusing, by way of example, the digitizer pointer 23 as described above.As each screw point 264 is digitized, its relative location with respectto the other acquired screw points 264 can be viewed in both sagittaland coronal views via the sagittal view panel 256 and the coronal viewpanel 258 as shown in FIG. 52. Optionally, the last screw pointdigitized may have a different graphic 266 than the previously-acquiredscrew points 264 (by way of example, the last screw point acquired 266may be a halo and the previously-acquired screw points 264 may becircles). The screws locations may be digitized from asuperior-to-inferior or inferior-to-superior direction and according tosome embodiments, the system 10 can detect which direction thedigitization is occurring in after the acquisition of two consecutivescrew point locations. If during the digitization process, the Userwishes to delete a digitized screw point, he/she may do so by pressingthe “Clear Point” button (not shown) under the Points menu 292. If theUser wishes to delete all digitized screw points, he/she may do so bypressing the “Clear All Points” button (not shown).

Once the digitized screw points 264 are deemed acceptable, the User maypress the “Calculate Rod” button 272 which initiates the curvecalculation preferably using one of the algorithms discussed in U.S.patent application Ser. No. 13/815,643, entitled “Systems and methodsfor performing spinal surgery” and filed on Mar. 12, 2013, the entirecontents of which are hereby incorporated by reference as if set forthfully herein. As shown for example in FIG. 53, once a rod solution hasbeen calculated, a rod graphic 274 populates through the screw points264, 266 and a confirmation graphic (e.g., a check) may appear on the“Acquire Screws” button 224 to indicate that the system 10 has generateda rod solution. Simultaneously, the “Calculate Rod” button 272 becomesthe “Undo Rod” button 272. If the User presses the “Undo Rod” button272, the rod solution 274 is cleared and the User may acquire more screwpoints or clear one or more screw points. After the “Undo Rod” button272 is pressed, it then changes back to the “Calculate Rod” button 272.Optionally, the system 10 may include a visual graphic for where along arod the curve calculation is generating a severe bend (acute angle). TheUser may select “Undo Rod” button 272, perform one or more surgicalmaneuvers (e.g. reduce the screw, backup the screw, adjust the screwhead, etc.), re-digitize the screw point, and generate a more feasiblesolution. As shown in FIG. 54, if the rod solution is acceptable to theUser, the Screw Acquisition step 1194 is complete and the system 10proceeds the Bend Instructions step 1196 in the flowchart of FIG. 49.Alternatively, although not shown the system 10 may display theoffending point resulting in the severe bend angle in red and offer thenext-best solution that includes a bend angle falling within apre-determined range of angles for that bender. If the rod solution isacceptable to the User, the Screw Acquisition step 1194 is complete andthe system 10 proceeds the Bend Instructions step 1196 in the flowchartof FIG. 49.

The User then selects the “Bend Instructions” button 226 which navigatesthe display screen 200 to a Bend Instructions (left or right) screenshown by way of example in FIG. 54. The bend instructions within thebend instructions panel 276 allows the User to view the bendinstructions corresponding to the resulting rod solution in the AcquireScrews screen. By way of example, the bend instructions panel 276contains three fields containing various aspects of the bendinginstruction: upper message field 278, bender instructions field 280, andlower message field 282. By way of example, the upper message field 278may communicate the rod cut length, rod type, and/or rod loadinginstructions to the User (e.g. “Cut Rod: 255.0 mm Load Inserter End IntoBender, Line Up”). The bender instructions field 280 displays rows 284of bend maneuvers in location 286, rotation 288, and bend angle 290 toperform on the mechanical bender 18 as will be described in greaterdetail below. In the example shown in FIG. 54, there are four rowsindicating four bend instructions. The lower message field 282 maycommunicate the direction of insertion or orientation of implanting therod to the User. For example, in some bend instructions the lowermessage field 282 may for example provide the following sampleinstruction: “Insert Rod head to foot.” In some implementations, the rodinsertion direction into the patient is dependent on the sequence ofscrew digitization (superior-to-inferior or inferior-to superior).According to one or more preferred embodiments, the bend instructionalgorithm takes into account the orientation of the inferior, superior,anterior, and posterior aspects of the rod and ensures that theseaspects are known to the User. As the instructions for use direct theUser to load the rod into the bender, the system 10 manages which bendsare imparted on the rod first based on the severity of the bend angles.The section of the bend instructions with greater bend angles may beperformed first then the straighter bend sections of the bendinstructions may be performed last. Further, the instructions may alsodirect the User to align a laser line or orientation line on the rod toan alignment arrow (not shown) on the mechanical rod bender 18. Thisalignment controls the Anterior/Posterior orientation of the rodgeometry and generates bend instructions accordingly. The User followsthe bend instructions generated by the system 10 for location (locationmay be color-coded on the bender 18 and on the screen 200 as greentriangle), rotation (rotation may be color-coded on the bender 18 and onthe screen 200 as red circle), and bend angle (bend angle may becolor-coded on the bender 18 and on the screen 200 as blue square),sequentially, starting at the first bend instruction and workingsequentially until the final bend is completed. From here, the User mayrepeat steps 1190-1198 on the rod construct for the contralateral sideof the patient's spine.

Within a surgical procedure, a User may wish to toggle between left andright screens to view left and right digitized screw points, rodpreviews, and bend instructions for reference or comparison. Selectingthe Left “L” toggle/status button 220 and right “R” toggle/status button222 allows the User to do so. According to one more implementations, theGUI may additionally include a History feature. Selecting the Historybutton (not shown) will allow the User to refer back to any previous rodbending solution. The User navigates to the Bend Instructions screen 226based on choice of the L/R toggle buttons 220, 222 and pressing the BendInstruction button 226. If navigating to previous bend instructions, theBend Instructions screen will display previous bend instructions. Oncethe User has selected the desired rod solution, the User then executesthe bends using the mechanical bender 18.

The embodiments described with respect to FIGS. 51-54 above contemplatedigitizing the implanted screw positions and outputting bendinstructions for a rod shaped to custom-fit within those implantedscrews. In one or more additional embodiments, the system 10 obtainsposition information of the implanted screws (steps 1192 and 1194),accepts correction inputs via one or more advanced options features(step 1195), and generates for viewing bend instructions for a rodshaped to fit at locations apart from those implanted screw positions(step 1196) as depicted in the flowchart of FIG. 55. Installing a rodshaped in this manner could correct a curvature or deformity in thepatient's spine according to a User's prescribed surgical plan. Detailsof the system 10 are discussed now discussed with examples for obtaininga rod bent according to one or more surgical plans.

As depicted in FIG. 56, selecting the “Points” button 292 expands a menufrom which the User may perform one or more corrections to the digitizedscrew points and the system 10 generates bend instructions that willachieve those desired corrections on the patient's spine once the rod isimplanted and the screws are brought to the rod.

In some surgical procedures, a User may wish that the rod bend solutionwill consider a point that is not a digitized screw point in determiningthe bend instructions. According to some implementations, this point isan adjusted distance from the digitized screw point location. Selectingthe “Adjust Points” button 296 from the Points menu 292 navigates theUser to an Adjust Points screen as depicted in FIG. 57. Selecting adigitized screw location of interest (for example the screw pointrepresented as dot 304 in FIG. 57) highlights the screw point and bringsup an adjust points control 306 in each of the sagittal and coronalviews 256, 258. The User adjusts point 304 to its desired location inthe sagittal and coronal planes using arrows 308, 310, 312, and 314. Insome implementations, as the point moves, dot 304 changes color based onthe distance from the originally digitized screw location as shown inFIG. 57. In some embodiments that color corresponds to color-codedoffset distance indicator (not shown) which provides visual feedback tothe User as to the distance the point has been adjusted. In someimplementations, the system 10 may have a maximum distance from thedigitized point past which it will not allow the manipulated point toexceed (by way of example only, this distance may be 5 mm). In otherimplementations, this distance may be depicted as a distance (forexample, the numeral 11 in FIG. 57, indicating that a screw point is 11mm from its original location). The User may adjust as many points asdesired in this fashion. The User may reset all adjusted points to theiroriginal configurations via “Reset” button 316. Once satisfied with theadjusted points, the User may either proceed to one or more additionaladvanced options as set forth below or select “Calculate Rod” 272. Once“Calculate Rod” 272 has been selected, the system 10 generates a rod inwhich the curve traverses the adjusted points, thereby creating acorrection-specific rod and providing the User with the ability tocorrect the curvature or deformity in the spine according to his or herprescribed curve.

In some instances, a User may want to align or correct the patient'sspine in the sagittal plane (i.e., add or subtract lordosis orkyphosis). The system 10 includes a sagittal correction feature in whichthe User is able to measure the amount of lordosis in the spine andadjust angles in the sagittal plane. The system 10 then incorporatesthese inputs into the bend algorithm such that the rod solution includesthe desired alignment or correction.

Selecting the “View Vectors” button (not shown) from the AdvancedOptions menu (not shown) initiates the sagittal correction feature asshown in FIG. 58. The User may select at least two points of interestand the system then determines the appropriate vector in the sagittalview. According to the embodiment shown in FIGS. 59-60, the angles aremeasured and adjusted based on the screw trajectory screw axis position)using the digitized screw data acquired in the Acquire Screws step 1194.As shown in FIG. 59, the User selects at least two screw points ofinterest (e.g., screw points 338 and 342). The system 10 then measuresthe angle between the screw trajectories. In some implementations, thesystem 10 may measure the total amount of lumbar lordosis by measuringthe lumbar lordosis angle 334 in the superior lumbar spine and thelumbar lordosis angle 336 in the inferior lumbar spine. Using the angleadjustment buttons 328, 330 on the Angle Adjustment Menu 326, the Usermay increase or decrease the desired angle correction of the spine inthe sagittal plane (i.e., add or subtract lordosis or kyphosissuperiorly or inferiorly). As the angle is adjusted, the angularposition 336 between the two screw points 338, 342 is changed as well.The system 10 may include a color-coded offset distance indicator 322 toprovide the User with an indication of the distance each digitized screwposition will be adjusted in the sagittal plane as described above. Oncethe desired amount of angular correction is achieved, the User mayselect the “Calculate Rod” button 272. The system 10 then displays a rodsolution 274 incorporating the User's clinical objective for correctionof the spine in the sagittal plane as depicted, for example, in FIG. 60.

According to one embodiment of the sagittal correction feature, thesuperior and inferior lumbar lordosis angles 354, 356 are measured,displayed, and adjusted referencing anatomy from an imported lateralradiographic image (not shown).

It is to be appreciated that, because patient position may have aneffect on the cervical and lumbar lordosis measurements, the sagittalcorrection feature of the system will be able to account for any patientpositioning-related deviations. It will also be appreciated that inaddition to lordotic corrections, the sagittal angle assessment tool maybe useful for other types of surgical maneuvers, including but notlimited to pedicle subtraction osteotomy (PSO) procedures and anteriorcolumn reconstruction (ACR) procedures.

In some instances, a User may want to align or correct the patient'sspine in the coronal plane (i.e., correct scoliosis). The system 10includes one or more coronal correction features in which the User isable to view the patient's spine (and deformity) in the coronal planevia anterior-posterior x-rays; measure one or more anatomic referenceangles; and/or persuade one or more screw locations towards a particularcoronal alignment profile by manually or automatically biasing whichdirection the rod bend curve is adjusted. The system 10 may thenincorporates these inputs into the bend algorithm such that the rodsolution includes the desired alignment or correction.

Selecting the “Coronal Straightening” button 302 initiates the coronalcorrection feature. The User may wish to ascertain the degree of coronaldeformity by referencing spinal anatomy, measuring the coronal Cobbangles between two anatomical references in the coronal plane, andadjusting those angles intraoperatively as part of the surgical plan tobring the spine into (or closer to) vertical alignment.

According to one or more other implementations of the coronal correctionfeature, as shown in FIG. 61, the User may select at least two points ofinterest and the system then generates a best fit reference line throughall points including and lying between the at least two points ofinterest. In some instances, the ideal correction of the spine in thecoronal plane is a straight vertical line extending between thesuperior-most and inferior-most screw locations of interest. However,depending on a patient's individual anatomy, achieving a straightvertical line may not be feasible. The User may wish to achieve acertain amount of correction relative to the ideal correction. From thedisplay screen, the User may select a percentage of relative correctionbetween the screw points as digitized 25%, 50%, 75% or 100% correctionto the best fit reference line. Furthermore, the system then calculatesa rod solution and shows an off-center indicator 322 to provide a Userwith an indication of the distance each screw is from thecoronally-adjusted rod construct as set forth above.

According to the embodiment shown in FIGS. 61-62, the User maystraighten all points within the construct (global coronal correction).From the display screen 200, the superior and inferior screw points 362,364 are selected and the system 10 generates a best fit global referenceline 366 through all points 362, 364, 368. Using the CoronalStraightening Menu 370, the User selects the degree of correctiondesired 372, 373, 374, 375 to adjust the percentage of correctiondesired. In the example shown in FIG. 62, the amount of desiredcorrection is shown as 100% on the percentage correction indicator 372,meaning the rod solution 274 will be a straight line in the coronalplane and all screw locations will be adjusted to fit the rod/line. Insome embodiments, the system 10 may include a color-coded offsetdistance indicator (not shown) to provide the User with an indication ofthe distance each digitized screw position will be adjusted in thecoronal plane as set forth above. If the User deems this an acceptablerod solution, the User selects the “Calculate Rod” button 272 to viewthe rod solution 274 and receive bend instructions or proceeds toanother advanced feature as will be described in greater detail below.

According to another embodiment, the User may straighten a subset of thescrew points within the construct (segmental coronal correction). Basedon the sequence those points are inputted into the system, a best-fitsegmental reference line is generated through the points in thedirection of the last chosen point. If an inferior point is selectedfirst and then a superior point is selected second, the system will drawthe best-fit segmental reference line superiorly. Conversely, if asuperior point is selected first and then an inferior point is selectedsecond, the system will draw the best-fit segmental reference lineinferiorly. Using the Coronal Straightening Menu, the User selects thepercentage of correction desired. The system may include a color-codedoffset distance indicator to provide the User with an indication of thedistance each digitized screw position will be adjusted in the coronalplane as set forth above. If the User deems this an acceptable rodsolution, the User selects the “Calculate Rod” button to view the rodsolution and receive bend instructions or proceeds to another advancedfeature as will be described in greater detail below.

According to another embodiment, segmental coronal correction may beachieved relative to the patient's central sacral vertical line (CSVL)instead of a best-fit segmental reference line running through twoselected digitized screw locations. The CSVL is the vertical linepassing through the center of the sacrum that may serve as the verticalreference line for the patient's coronal deformity as well as a guidefor spinal correction in the coronal plane in accordance with thecoronal assessment and correction features of the present disclosure.

According to another embodiment, as shown in FIGS. 63-65, in some cases,the rod may traverse the thoracic and cervical vertebra. In suchembodiments, the appropriate rod may be a 5.5 mm to 3.5 mm transitionrod to allow use of a smaller rod with the smaller screws in thecervical region, and a larger rod in the thoracic region for increasedstability. It is necessary to identify the point of transition so thatthe rod may be properly bent for each region. As shown in FIG. 63, fromthe Points menu, the User will select the Transition Point button 293.The User will then identify the most inferior 3.5 mm screw 295. Once thetransition point 295 is selected, all of the points 297 superior to thetransition point will be smaller in size to indicate the smaller screwsand rod in that region as shown in FIG. 64. The User may change thetransition point 295 by selecting another point. Once the location ofthe transition screw point 295 is deemed acceptable, the User may pressthe “Calculate Rod” button 272 which initiates the curve calculationpreferably using one of the algorithms discussed above. Once a rodsolution has been calculated, a rod graphic 274 populates through thescrew points 264, 295, 297 and a confirmation graphic (e.g., a check)may appear on the “Acquire Screws” button 224 to indicate that thesystem 10 has generated a rod solution. The graphic will show a larger5.5 mm rod at the inferior screw points, 3.5 mm rod at the superiorscrew points, and the transition aligned at the selected transitionpoint 295 as shown for example in FIG. 65. An exemplary set of bendinstructions for a transition rod is shown in FIG. 66. The instructiondirect the User to cut 30 mm off the 3.5 mm end and cut 157.5 mm of the5.5 mm end. The cut to both ends ensures that the transition is alignedat the selected transition point 295.

As shown in FIGS. 67-69, in some surgical procedures it may be necessaryto add an offset connector to a cervical construct. The User may selectthe Points button 292 to access the menu. The User may then select theOffset connector button 294. The User may then select a point 299 to addan offset connect to that screw. The display will indicate the offsetconnector 301 as line connecting the selected point and the offset point303. The offset point may be adjusted using the directional arrows. Thedisplay will indicate the distance between the selected point and theoffset point as shown, for example in FIG. 68. Once satisfied with theadjusted points, the User may select “Calculate Rod” 272. Once“Calculate Rod” 272 has been selected, the system 10 generates a rod 274in which the curve traverses the adjusted points, thereby creating aoffset-specific rod as shown in FIG. 69.

From one or many of the features discussed above, once the User hasselected the desired rod solution, the User then executes the bendsusing a mechanical rod bender 18 like the embodiment depicted, forexample in FIG. 70. It is contemplated that the mechanical rod bender 18may be any bender that takes into account six degrees of freedominformation as it effects bends onto a spinal rod. By way of example,according to one implementation, the mechanical rod bender 18 may be thebender described in commonly-owned U.S. Pat. No. 7,957,831 entitled“System and Device for Designing and Forming a Surgical Implant”patented Jun. 7, 2011, the disclosure of which is hereby incorporated byreference as if set forth in its entirety herein. According to a secondimplementation, the mechanical rod bender 18 may be the bender shown inFIG. 65. First and second levers 1106, 1110 are shown as is lever handle1108 designed for grabbing the lever 1106 manually and a base 1112 forholding lever 1110 in a static position. Second lever 1110 has a rodpass through 1114 so that an infinitely long rod can be used as well assteady the rod during the bending process with the rod bending device18. The User grabs handle 1108 and opens it to bend a particular rod bypicking an angle on the angle gauge 1132 and closing the handle 1108such that levers 1106, 1110 are brought closer together. The mechanicalrod bender 18 in other embodiments could be produced to bend the rodduring the handle opening movement as well. The rod moves throughmandrel 1118 and in between moving die 1120 and fixed die 1122. The rodis bent between the two dies 1120, 1122. Gauges on the bender 18 allowthe User to manipulate the rod in order to determine bend position, bendangle, and bend rotation. The rod is held in place by collet 1126. Bysliding slide block 1128 along base 1112, the rod can be movedproximally and distally within the mechanical rod bender 18. Positionmay be measured by click stops 1130 at regular intervals along base1112. Each click stop 1130 is a measured distance along the base 1112and thus moving a specific number of click stops 1130 gives one aprecise location for the location of a rod bend.

The bend angle is measured by using angle gauge 1132. Angle gauge 1132has ratchet teeth 1116 spaced at regular intervals. Each ratchet stoprepresents five degrees of bend angle with the particular bend anglegauge 1132 as the handle 1106 is opened and closed. It is to beappreciated that each ratchet step may represent any suitable degreeincrement (e.g., between 0.25 degrees to 10 degrees). The bend rotationis controlled by collet knob 1134. By rotating collet knob 1134 eitherclockwise or counterclockwise, the User can set a particular rotationangle. The collet knob 1134 is marked with regular interval notches 1136but this particular embodiment is continuously turnable and thus hasinfinite settings. Once a User turns knob 1134, the User can set theknob 1134 at a particular marking or in between or the like to determinea particular angle rotation to a high degree of accuracy. Additionally,base 1112 may have a ruler 1138 along its length to aid the User inmeasuring a rod intraoperatively.

According to another implementation, the rod bender 18 may be apneumatic or motor-driven device which automatically adjusts thelocation, rotation and bend angle of the rod. By way of example, threemotors may be utilized for each movement. A linear translator motorwould move the rod in and out of the mandrel 1118 and moving die 1120.One rotational motor would rotate the rod and moving die 1120. The bendcalculations could be converted into an interface program that would runto power and control the motors. The automated bender would lessen thepossibility of User error in following the manual bend instructions. Itwould also increase the resolution or number of bends that can beimparted in the rod making for a smoother looking rod.

Method for Global Alignment

The flowchart in FIG. 71 provides an overview of an exemplary method formeasuring, planning, and generating rod bending instructions for a moreglobally aligned spine. Briefly, according to one embodiment, one ormore preoperative images of the spinal column are acquired (step 1200).Using a planning software and interface, the User inputs the images andmeasures the preoperative spinal parameters, which may include PI, LL,Superior LL, Inferior LL, C7PL, and TK in the thoracolumbar region andCL, ΔCL, TS, CSVA, and CBVA in the cervical region (step 1202). The userplans the surgical intervention to correct the defect, includingdetermining optimal spinal parameters for a globally aligned spine (step1204). If the User is satisfied with the surgical plan, the plannedspinal parameter values are saved. When the patient is prepared forsurgery, the pre-operative and planned spinal values are input into thesystem 10 (step 1206). The surgeon performs spinal surgery to correctthe defect using the surgical plan as a guide as to appropriate implantsand placement of screws and/or plates. During the surgery, the user mayemploy neuromonitoring systems. At any point during the surgery, butgenerally after placement of the implants and/or insertion of the screwsor hoods for rod stabilization, the User will acquire intraoperativeimages of the spine and measure the spinal parameters taken duringpreoperative planning (step 1208). The measurement of spinal parameterswill inform the surgeon as to the current state of the patient'salignment, provide a comparison to the pre-surgery deformity and/or theplanned correction (step 1210). If the intraoperative surgicalparameters differ from non-pathologic ranges, or if they differ from theplanned values, the surgeon may undertake corrective measures including,for example, replacing the implants. The surgeon may make additionalintraoperative assessments of the spinal parameters until the spine isaligned to the satisfaction of the surgeon (step 1208). The user thenmeasures the location of each of the screws for the placement of the rod(step 1212). The user may make manual adjustments to the locations ofthe screws to correct the placement, and introduce additional lordosisor kyphosis, or correct other spinal misalignments. It will beappreciated that the intraoperative measurements of alignment andcorrective adjustments to implants and screws may be repeated until thedesired degree of alignment has been achieved.

Once the surgeon is satisfied that the screws are properly placed andlocated in the surgical software, rod bending instructions can begenerated (step 1214). The rod bending instructions are used as atemplate for bending the rod using a mechanical bender (step 1214). Whena properly bent rod has been formed, the rod is implanted in the patientand secured into the screws by a set screw. If desired, the surgeon mayoptionally perform additional intraoperative assessment of spinalalignment to confirm that the spinal surgery has corrected, to theextent desired or possible, deformity of the spine and has restored thepatient's spinal alignment. When the surgeon is satisfied with thealignment, the surgery is completed.

We claim:
 1. A system for global alignment of a spine during spinalsurgery, the system comprising an imaging device, a spatial trackingsystem, a control unit, and a bending device.
 2. A system for use duringa surgical procedure, the system comprising: an imaging device; a rodbending device; a control unit configured to: obtain one or morepreoperative measurements of an anatomical parameter of a patient;obtain one or more planned target measurements of the anatomicalparameter; obtain an intraoperative image from the imaging device;measure an intraoperative measurement of the anatomical parameter; andcalculate an instruction for bending a surgical rod.
 3. The system ofclaim 2, wherein the anatomical parameter is a chin brow vertical angle.4. The system of claim 3, wherein the chin brow axis is an angle of apatient's gaze relative to a horizontal position.
 5. The system of claim4, wherein the control unit displays to a user a color indication of theangle of the gaze.
 6. The system of claim 2, wherein the anatomicalparameter is a parameter correlated to a health related quality of lifescore.
 7. The system of claim 2, wherein the anatomical parameter is aparameter correlated to the alignment of a patient's head over thepatient's pelvis.
 8. A method for assessing global alignment of thespine during a surgical procedure, the method comprising: inputting aplanned target value of one or more spinal parameters into a controlunit; capturing one or more intraoperative fluoroscopy images into thecontrol unit; measuring an intraoperative value of the one or morespinal parameters; comparing the intraoperative value of the one or morespinal parameters with the planned target value of the spinalparameters; measuring a location of one or more screws; calculating aninstruction to bend a rod to the location of the one or more screws; andbending the rod according to the instruction.
 9. The method of claim 8,wherein at least one of the spinal parameters is a chin brow verticalangle.
 10. The method of claim 8, wherein the method further compriseslocating a point on the brow, locating a point on the chin, calculatinga line between the points, and calculating an angle between the line anda vertical axis.
 11. The method of claim 8 further comprising,calculating a preoperative value of the one or more spinal parameters.12. The method of claim 8 further comprising, calculating a secondtarget value for the one or more spinal parameters based on thecomparison of the intraoperative value with the planned target value.13. The method of claim 8, wherein at least one of the spinal parametersis a parameter correlated to a health related quality of life score. 14.The method of claim 8, wherein the spinal parameter is a parametercorrelated to the alignment of a patient's head over the patient'spelvis.
 15. The method of claim 8, wherein at least one of the spinalparameters is cervical sagittal vertical axis.
 16. The method of claim8, wherein at least one of the spinal parameters is T1 slope.
 17. Themethod of claim 8, wherein at least one of the spinal parameters iscervical lordosis.